This proposal utilizes Drosophila models for investigating mechanisms and functions of the tumor suppressor gene neurofibromatosis 1 (NF1). We are particularly interested in its role in regulation of G-protein-dependent activation of the cAMP pathway. NF1 protein contains a fragment homologous to catalytic domain of the Ras-specific GAPS and its mutations cause a common neurogenetic disorder that is identified by neurofibromas and other symptoms including specific learning defects. Our study of Drosophila NF1 mutants has revealed that in addition to as a Ras-GAP, NF1 is involved in regulation of G-protein dependent activation of adenylyl cyclase (AC) encoded by rutabaga gene. This NF1-regulated cAMP pathway is crucial for mediating a neuropeptide response at neuromuscular junction, body size development, and learning and memory. However, it is unclear how NF1 regulates AC activity, how the NF1-regulated AC pathway contributes to learning and memory, and whether such NF1-regulated mechanism also works in vertebrates. The proposal is intended to investigate these problems. It includes two specific aims. 1) Eighteen point mutations identified in human NF1 patients will be used to define which parts of NF1 is important for regulation of AC activity and whether Ras is involved in such regulation. Then mouse Nf1 knockout mutants will be used to assay whether NF1 can regulate AC activity in vertebrates. 2) Biochemical and electrophysiological analyses will be directed to determine neurotransmitters that activate NF1-regulated AC activity in the fly brain and neurotransmitters that activate the NF1-regulated AC pathway to modulate membrane currents in identified mushroom body neurons. These neurons have been suggested to be involved in the associative learning process that are disrupted by NF1 mutations. We expect that the proposed research will lead to new insights into NF1 function and provide new clues for understanding pathogenesis of NF1.